In some lighting arrangements, wavelength converting materials are used together with narrow-bandwidth light sources for producing light of a particular color, typically white light. The basic principle of one such technique is to use the light sources to photoexcite the wavelength converting material which then emits light in a wavelength range such that the combination of that light and light from the light sources that has not been converted appears white.
A common example of lighting arrangements based on this technique are so-called remote phosphor systems in which the wavelength converting material is a phosphor arranged at a distance from the light sources, usually light-emitting diodes (LEDs). It is common to provide such lighting arrangements with blue LEDs and to have the light of the LEDs mix with a predominantly yellow light emitted by the phosphor so that white light is formed.
An example of a remote phosphor system is the tubular blue LED lamp with remote phosphor disclosed in U.S. Pat. No. 7,618,157 B1. This lamp has LEDs arranged on a linearly extending heat sink and enclosed by a plastic cover with phosphor.
In many domestic, commercial, industrial and other applications, it is desirable that the lighting arrangement deliver a uniform illumination. There is a need to improve existing lighting arrangements in this respect.